Medium access control layer architecture for supporting enhanced uplink

ABSTRACT

A method and apparatus for enhanced uplink communication is disclosed. A Node-B receives a scheduling request from a wireless transmit/receive unit (WTRU). The Node-B determines a scheduling grant based at least on the scheduling request. The Node-B transmits the scheduling grant to the WTRU. The Node-B demultiplexes a received medium access control for enhanced uplink (MAC-e) protocol data unit (PDU), from the WTRU, into medium access control for dedicated channel (MAC-d) PDUs. The Node-B generates and sends a transmission feedback in response to the received MAC-e PDU.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/336,737, filed Jul. 21, 2014, which is a continuation of U.S. patentapplication Ser. No. 13/599,421, filed Aug. 30, 2012, which issued onAug. 12, 2014, as U.S. Pat. No. 8,805,354, which is a continuation ofU.S. patent application Ser. No. 11/117,626, filed on Apr. 28, 2005,which issued on Sep. 4, 2012, as U.S. Pat. No. 8,259,752, which claimsthe benefit of U.S. Provisional Application Nos. 60/568,944, filed May7, 2004, and 60/578,533, filed Jun. 10, 2004, all of which areincorporated by reference as if fully set forth.

FIELD OF INVENTION

The present invention is related to a wireless communication systemincluding a wireless transmit/receive unit (WTRU) and a Node-B. Moreparticularly, the invention is related to medium access control (MAC)layer architecture and functionality for supporting enhanced uplink (EU)in the wireless communication system.

BACKGROUND

Methods for improving uplink (UL) coverage, throughput and transmissionlatency are being investigated in Release 6 of the Third GenerationPartnership Project (3GPP). In order to successfully implement thesemethods, scheduling and assigning of UL physical resources have beenmoved from a radio network controller (RNC) to the Node-B such that theNode-B can make decisions and manage UL radio resources on a short-termbasis more efficiently than the RNC, even if the RNC retains overallcontrol of the Node-B.

One or more independent UL transmissions are processed on the enhanceddedicated channel (E-DCH) between the WTRU and a universal mobiletelecommunication systems (UMTS) terrestrial radio access network(UTRAN) within a common time interval. One example of this is a MAClayer hybrid-automatic repeat request (H-ARQ) or a simple MAC layer ARQoperation where each individual transmission may require a differentnumber of retransmissions to be successfully received by the UTRAN.

SUMMARY

A method and apparatus for processing enhanced uplink data is disclosed.A request for uplink resources is transmitted, wherein the request foruplink resources is a request to transmit data over an enhanceddedicated channel (E-DCH). An uplink scheduling grant is received inresponse to the request for uplink resources. Data from medium accesscontrol for dedicated channel (MAC-d) flows is multiplexed into a mediumaccess control for enhanced uplink (MAC-e) protocol data unit (PDU). Atransport format combination (TFC) is selected for transmission of theMAC-e PDU. The MAC-e PDU is transmitted over the E-DCH using anidentified hybrid automatic repeat request (H-ARQ) process. Feedbackinformation is received in response to the transmitted MAC-e PDU. TheMAC-e PDU is retransmitted using the identified H-ARQ process on acondition that the feedback information indicates a negativeacknowledgment (NACK) of the MAC-e PDU transmission.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding of the invention may be had from thefollowing description of a preferred embodiment, given by way of exampleand to be understood in conjunction with the accompanying drawingwherein:

FIG. 1 is a block diagram of a wireless communication system inaccordance with the present invention;

FIG. 2 is a block diagram of a protocol architecture of a WTRU inaccordance with the present invention;

FIG. 3 is a block diagram of MAC-e architecture in a WTRU in accordancewith the present invention;

FIG. 4 is a block diagram of MAC-e architecture in a Node-B inaccordance with the present invention; and

FIG. 5 is a block diagram of MAC-e architecture of a WTRU and a Node-Balong with signaling process between the WTRU and the Node-B inaccordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereafter, the terminology “WTRU” includes but is not limited to a userequipment, a mobile station, a fixed or mobile subscriber unit, a pager,or any other type of device capable of operating in a wirelessenvironment. When referred to hereafter, the terminology “Node-B”includes but is not limited to a base station, a site controller, anaccess point or any other type of interfacing device in a wirelessenvironment.

The features of the present invention may be incorporated into anintegrated circuit (IC) or be configured in a circuit comprising amultitude of interconnecting components.

FIG. 1 is a block diagram of a wireless communication system 10 inaccordance with the present invention. The system 10 comprises a WTRU100, a Node-B 200 and an RNC 300. The RNC 300 controls overall EUoperation by configuring EU parameters for the Node-B 200 and the WTRU100 such as initial transmit power level, maximum allowed EU transmitpower or available channel resources per Node-B. Between the WTRU 100and the Node-B 200, an E-DCH 102 is established for supporting EUtransmissions.

For E-DCH transmissions, the WTRU 100 sends a rate request to the Node-B200 via an UL EU signaling channel 104. In response, the Node-B 200sends a rate grant to the WTRU 100 via a downlink (DL) EU signalingchannel 106. After EU radio resources are allocated for the WTRU 100,the WTRU 100 transmits E-DCH data via the E-DCH 102. In response to theE-DCH transmissions, the Node-B sends an acknowledge (ACK) ornon-acknowledge (NACK) for H-ARQ operation via the DL EU signalingchannel 106. The Node-B 200 may also respond with rate grants to theWTRU 100 in response to E-DCH data transmissions.

FIG. 2 is a block diagram of protocol architecture of the E-DCH 102 inaccordance with the present invention. A new MAC entity for EU calledMAC-e is created in the WTRU 100, the Node-B 200 and the RNC 300 tohandle all functions related to the transmission and reception of anE-DCH. A MAC-e entity 120 is incorporated into the WTRU 100 between aMAC-d entity 130 and a physical layer (PHY) entity 110. The MAC-e 120 inthe WTRU handles H-ARQ transmissions and retransmissions, priorityhandling, MAC-e multiplexing, and TFC selection. A MAC-e 220 entity isincorporated into the Node-B 200 which handles H-ARQ transmissions andretransmissions, E-DCH scheduling and MAC-e demultiplexing. A MAC-eentity 320 is incorporated into the RNC 300 to provide in-sequencedelivery and to handle combining of data from different Node-Bs.

FIG. 3 is a block diagram of the MAC-e 120 architecture in a WTRU 100 inaccordance with the present invention. The WTRU MAC-e 120 comprises anEU rate request/assignment entity 122, a priority handling entity 124, aTFC selection entity 126 and an H-ARQ entity 128. It should be notedthat FIG. 3 is provided as an example of preferred embodiment of thepresent invention and that the entities shown in FIG. 3 may beincorporated into a common MAC functional entity and that the functionsmay be implemented by more or less functional entities.

The EU rate request/assignment entity 122 is responsible for requestingradio resources from the Node-B 200 when the WTRU 100 has E-DCH datawaiting to be transmitted via the E-DCH 102. The EU rate request couldbe one of a traffic volume indicator, a requested data rate, a TFCindex, and traffic volume measurement (TVM) quantities for each dataflow. The rate request can be sent to the Node-B 200 via either physicalor MAC layer signaling. Rate requests are generated based on radio linkcontrol (RLC) data TVM. The TVM may include traffic volume of data forE-DCH transmissions or optionally may further include data awaitingretransmission with active H-ARQ processes.

When the WTRU 100 receives a rate grant (i.e., rate and/or timescheduling) from the Node-Bs 200 (the WTRU may receive the rate grantfrom more than one Node-B), the EU rate request/assignment entity 122notifies the priority handling entity 124 that resources are availablefor transmission of the data. The received rate grants determine theE-DCH transport format combination set (TFCS) subset, and/or start time,and duration (optional).

By sending the rate request, the WTRU 100 may ask the Node-B 200 tochange the set of allowed UL TFCs within the TFCS, and the Node-B 200can change the allowed UL TFCs within the TFCS by sending the rategrant. The WTRU 100 may send a scheduling information update to theNode-B 200 to provide buffer occupancy and/or available transmit powerinformation so that a scheduling entity 222 in the Node-B 200 maydetermine appropriate TFCS indicator and transmission time interval. Forfast rate scheduling by persistency control, the Node-B 200 may sendparameters that represent the available interference the system cantolerate and thus prevent WTRUs in rate control mode from introducingadditional interference. One way this can be accomplished is for theNode-B 200 to signal the allowed transmit power the WTRU 100 may use forEU transmissions in the rate grant.

The priority handling entity 124 manages the assignment of data flowsand H-ARQ processes according to the priority of the data. Based ontransmission feedback from associated DL EU signaling, either a newtransmission or retransmission is determined. Furthermore, a queueidentity (ID) and transmission sequence number (TSN) for each MACprotocol data unit (PDU) is determined. The TSN is unique to eachpriority class within an E-DCH, and is incremented for each new datablock. Optionally, the priority handling entity 124 may preemptretransmission of lower priority data. A new transmission of higherpriority data can be initiated instead of a pending retransmission oflower priority data at any time to support priority handling.

The TFC selection entity 126 selects a TFC for the data to betransmitted on the E-DCH 102 according to the information signaled inthe rate grants, and multiplexes multiple MAC-d flows into one MAC-ePDU. The rate grant may be either absolute grant or relative grant. Theabsolute grant provides an absolute limitation of the maximum amount ofUL resources that the WTRU may use. The relative grant increases ordecreases the resource limitation compared to the previously used value.

The TFC selection is subject to maximum allowed transmit power, and thecorresponding TFCS subset allowed by the rate grants from the Node-B200. TFC selection is based on logical channel priorities such that theTFC selection maximizes the transmission of higher priority data. Theallowed combinations of MAC-d flows in one MAC-e PDU, which isconfigured by the RNC, are also considered in selecting the TFC.

The H-ARQ entity 128 handles all the tasks that are required for H-ARQprotocols. The H-ARQ entity 128 is responsible for storing MAC-epayloads and retransmitting them in the case of a failed transmission.The H-ARQ entity 128 may support multiple instances, (H-ARQ processes),of the H-ARQ protocol. There may be more than one H-ARQ process for theEU configured at the WTRU 100.

In accordance with the present invention, a synchronous H-ARQ ispreferably implemented. Therefore, H-ARQ operation is based onsynchronous DL ACK and NACK and synchronous retransmissions in the UL.

FIG. 4 is a block diagram of MAC-e 220 architecture in a Node-B 200 inaccordance with the present invention. The Node-B MAC-e 220 comprises ascheduler 222, a demultiplexer 224 and an H-ARQ entity 226. In theNode-B, one MAC-e entity 220 is preferably provided for each WTRU andone scheduler is preferably provided for each cell. The scheduler 222manages E-DCH cell resources between WTRUs.

The scheduler 222 manages E-DCH resources between WTRUs and H-ARQprocesses. Based on rate requests from WTRUs 100, the scheduler 222generates rate grants and sends them to the WTRUs 100 via DL EUsignaling channels 106. The rate grant provides information thatdetermines the set of TFCs from which the WTRU 100 may choose andindicates the maximum resource that a WTRU is allowed to use for E-DCHtransmissions. The scheduler 222 controls reception of rate request andtransmission of rate grants on a corresponding EU signaling channel.Alternatively, a separate control entity (not shown) may be provided inthe Node-B MAC-e 220 for reception of the rate requests and transmissionof rate grants and the scheduler 222 may be provided out of the Node-BMAC-e 220.

The demultiplexer 224 demultiplexes MAC-e PDUs into MAC-d PDUs. MAC-dflow to MAC-e PDU multiplexing is supported in the WTRU 100. MultipleMAC-d flows can be configured for one WTRU and can be multiplexed in thesame MAC-e PDU. The combination of MAC-d flows that can be multiplexedin one MAC-e PDU is configured by the RNC 300. The multiplexed MAC-ePDUs are demultiplexed into MAC-d flows by the demultiplexer 224. TheNode-B demultiplexing may result in MAC-d or RLC PDU reordering, andMAC-e PDU reordering may be performed by the RNC 300.

Reordering may be performed either in the Node-B MAC-e where the H-ARQprocess number is known, or in the RNC MAC-e. Referring back to FIG. 2,the RNC MAC-e 320 includes a reordering entity for reordering receivedMAC-e PDUs according to the received transmission sequence number (TSN).MAC-e PDUs with consecutive TSNs are delivered to the disassemblyfunction and PDUs with a missing lower TSN are not delivered to thedisassembly function. The disassembly function removes the MAC-e headerbefore sending it to a higher layer. The RNC 300 includes a plurality ofreordering queues for reordering PDUs with different priority classes.

In the case that the reordering is performed in the RNC MAC-e, theNode-B 200 passes the H-ARQ process number with the successfully decodeddata to the RNC 300. The H-ARQ process may also be implicitly known bythe time of reception at Node-B passed to the RNC. The H-ARQ processnumber may be implicitly derived from either a system frame number (SFN)or a connection frame number (CFN) along with the knowledge of the H-ARQprocess allocation scheme in the WTRU 100.

The H-ARQ entity 226 generates ACKs and NACKs indicating the deliverystatus of E-DCH transmissions. One H-ARQ entity may support multipleinstances of stop and wait H-ARQ protocols.

FIG. 5 is a block diagram of MAC-e architecture of a WTRU 100 and aNode-B 200 along with signaling processes between the WTRU 100 and theNode-B 200 in accordance with the present invention. When the WTRU MAC-e120 receives data from WTRU RLC layer 140 to be transmitted via an E-DCH102 at step 502, the EU rate request entity 122 sends a rate request tothe Node-B 200 (step 504). The Node-B 200 responds with a rate grant(step 506). Upon receipt of the rate grant, the EU rate request entity122 notifies the priority handling unit 124 that radio resources areavailable for transmission of the data (step 508). The priority handlingunit 124 then multiplexes data and assigns an H-ARQ process according tothe priority of the data, and a TFC for the data is selected by the TFCselection entity (steps 510, 512). The data is transmitted with theassigned H-ARQ process via the E-DCH 102 (step 514). The Node-B 200sends a feedback signal through DL EU signaling channel 106 (step 516).If the feedback is a NACK, the data may be autonomously retransmitted(step 518), or may be retransmitted after another rate grant is received(step 520).

Although the features and elements of the present invention aredescribed in the preferred embodiments in particular combinations, eachfeature or element can be used alone without the other features andelements of the preferred embodiments or in various combinations with orwithout other features and elements of the present invention.

While the present invention has been described in terms of the preferredembodiment, other variations which are within the scope of the inventionas outlined in the claims below will be apparent to those skilled in theart.

What is claimed is:
 1. A Node-B that communicates with a wirelesstransmit/receive unit (WTRU) over an enhanced uplink channel, the Node-Bcomprising: a controller configured to receive a scheduling request froma WTRU; a scheduler configured to determine a scheduling grant based atleast on the scheduling request; the controller configured to transmitthe scheduling grant to the WTRU; a demultiplexer configured todemultiplex a received medium access control for enhanced uplink (MAC-e)protocol data unit (PDU), from the WTRU, into medium access control fordedicated channel (MAC-d) PDUs; and a hybrid automatic repeat request(H-ARQ) entity configured to generate and send a transmission feedbackin response to the received MAC-e PDU, wherein the H-ARQ entity supportsa plurality of H-ARQ processes, wherein the H-ARQ processes aresynchronized between the Node-B and the WTRU.
 2. The Node-B of claim 1wherein the scheduling grant is an absolute grant, which provides anabsolute limitation of the maximum amount of uplink resources that theWTRU may use.
 3. The Node-B of claim 1 wherein the scheduling grant is arelative grant, wherein the relative grant specifies an amount by whicha current amount of uplink resources is increased or decreased.
 4. TheNode-B of claim 1 wherein the scheduling request includes informationregarding a volume of enhanced uplink data.
 5. The Node-B of claim 1wherein the received MAC-e PDU comprises data determined by the WTRUbased on allowed combinations of MAC-d flows.
 6. The Node-B of claim 1wherein the Node-B comprises a MAC-e entity.
 7. The Node-B of claim 6wherein the MAC-e entity comprises the controller, the demultiplexer,and the H-ARQ entity.
 8. The Node-B of claim 7 wherein there is oneMAC-e entity in the Node-B for each WTRU that transmits data over anenhanced uplink channel to the Node-B.
 9. The Node-B of claim 1 whereinthe scheduler manages enhanced uplink resources between WTRUs in a cell.10. A method implemented by a Node-B, wherein the Node-B communicateswith a wireless transmit/receive unit (WTRU) over an enhanced uplinkchannel, comprising: receiving a scheduling request from a WTRU;determining a scheduling grant based at least on the scheduling request;transmitting the scheduling grant to the WTRU; demultiplexing a receivedmedium access control for enhanced uplink (MAC-e) protocol data unit(PDU), from the WTRU, into medium access control for dedicated channel(MAC-d) PDUs; generating a transmission feedback in response to thereceived MAC-e PDU; and transmitting the transmission feedback to theWTRU, wherein the Node-B supports a plurality of hybrid automatic repeatrequest (H-ARQ) processes, wherein the H-ARQ processes are synchronizedbetween the Node-B and the WTRU.
 11. The method of claim 10 wherein thescheduling grant is an absolute grant, which provides an absolutelimitation of the maximum amount of uplink resources that the WTRU mayuse.
 12. The method of claim 10 wherein the scheduling grant is arelative grant, wherein the relative grant specifies an amount by whicha current amount of uplink resources is increased or decreased.
 13. Themethod of claim 10 wherein the scheduling request includes informationregarding a volume of enhanced uplink data.
 14. The method of claim 10wherein the received MAC-e PDU comprises data determined by the WTRUbased on allowed combinations of MAC-d flows.
 15. The method of claim 10wherein the Node-B comprises a MAC-e entity.
 16. The method of claim 15wherein the MAC-e entity comprises a controller, a demultiplexer, and aH-ARQ entity.
 17. The method of claim 16 wherein there is one MAC-eentity in the Node-B for each WTRU that transmits data over an enhanceduplink channel to the Node-B.
 18. The method of claim 10 wherein theNode-B comprises a scheduler and the scheduler manages enhanced uplinkresources between WTRUs in a cell.